Author: Christopher Conkie
Date: 17:20:21 02/23/06
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On February 23, 2006 at 16:12:47, Steffan Westcott wrote: >On February 23, 2006 at 15:02:25, Christopher Conkie wrote: > >>>>Is there a way to keep board representations entirely in hexadecimal format >>>>until output of moves are required. How would one accomplish rotation for >>>>diagonals without conversion. For example, is it needed to convert pieces to a >>>>number if you started with something like..... >>>> >>>>typedef unsigned long long bitboard; >>>> >>>>bitboard B_Occ = 0xffff000000000000ULL; >>>>bitboard W_Occ = 0x000000000000ffffULL; >>>> >>>>bitboard All_P = 0x00ff00000000ff00ULL; >>>>bitboard All_N = 0x4200000000000042ULL; >>>>bitboard All_B = 0x2400000000000024ULL; >>>>bitboard All_R = 0x8100000000000081ULL; >>>>bitboard All_Q = 0x1000000000000010ULL; >>>>bitboard All_K = 0x0800000000000008ULL; >>>> >>>>I have been toying with this idea but am not quite sure of the validity of it's >>>>basis. I was thinking that if less conversion took place it would improve speed >>>>significantly. >>>> >>>>Any thoughts would be nice. > >[snip] > >>I am looking at ways to improve speed without having to use arrays to >>rotate for diagonals. >> >>There is a max of 7 squares in any one specific horizontal, vertical or diagonal >>direction for a piece to move to. If we know that, why not have a table that >>looks at each of the 8 directions and subsequent squares in turn until a >>friendly or opposing piece is found and deal with that accordingly. This would >>require a table that is stepped through consisting of the 56 values that shift >>up, down or across. > > >Christopher, > >I cannot comment if the 'purist' bitboard approach is the fastest method >available for typical manipulations required in a chess engine. However, I have >adopted this approach to better support a 'regular' pattern matching framework, >and common subexpression elimination. I postpone bit scanning/serialisation (and >conversion to square co-ordinates) as much as possible. Yes, this is exactly my thought too. > >You may find an old post of mine of interest, which talks about direct >generation of attack/move bitboards for sliding pieces which also takes >occluders (blocking pieces) into account: >http://chessprogramming.org/cccsearch/ccc.php?art_id=261956 There are no >rotated bitboards nor lookup tables used. > >Cheers, >Steffan That is very interesting. There is alot of good stuff in your post and that thread as a whole. Thank you for pointing me towards that. Christopher
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